The present embodiments relate to a method and control unit for activating actuators of a vehicle during emergency operation.
In the future, vehicles with electric main engines will be widespread. An electric main engine may be operated with a voltage range of 100 to 800 V for vehicles with an electric or hybrid drive. This represents a high voltage in comparison with the usual on-board electrical systems of motor vehicles, which may operate in a voltage range of 12 to 24 volts.
An on-board electrical system dedicated to the main engine may be referred to as a high-voltage network, and an on-board electrical system operating in the usual voltage range may be referred to as a low-voltage network. In this kind of electric or hybrid vehicle, high-voltage networks and low-voltage networks are combined into a multi-voltage on-board electrical system.
Electric or hybrid vehicles may be equipped with a drive energy store, which is dedicated to the high-voltage circuit of the vehicle. The drive energy store is thus also referred to as a high-voltage energy store.
The drive energy store may underlie comprehensive diagnostic measures both during and also outside of the driving operation. For example, a fault in the drive energy store and a thereby shortened remaining driven distance is to be indicated promptly to a vehicle driver so that the vehicle does not come to a halt in a remote area due to an empty drive energy store. It is thus to be assumed that the drive energy store is a sufficiently well monitored component in the vehicle.
Failure of the drive energy store may result in dramatic consequences if the vehicle is equipped exclusively with electrically-actuatable brake and/or steering actuators (e.g., “brake-by-wire” and “steer-by-wire,” respectively).
The brake actuators indicated render conventional brake hydraulics superfluous. The vehicle driver nevertheless actuates a brake pedal of the vehicle as normal (e.g., presses against a spring or spring force generated by the spring, which simulates the normal feeling of a pedal). In a control unit of the vehicle, a brake force for each wheel of the vehicle is calculated herefrom. A contact force is generated on the individual wheels from brake pads of the brake unit on a brake disk by an electromechanical unit including an electric motor and spindle.
The steering actuators mentioned render conventional transmission mechanisms such as steering links superfluous. A steering command applied to the steering device by the vehicle driver is not directly mechanically applied to the steering gear and thereby eventually to the wheels to be steered, but rather indirectly via a steering actuator.
For reasons of synergy, the drive energy store may also draw on the electrically-actuatable braking and steering actuators for energy supply. As the drive energy store is sufficiently well monitored, the energy supply of the electrically-actuatable actuators is provided during normal driving operation.
Sudden failure of the drive energy store when the vehicle is at full speed would however result in the steering or braking commands from the vehicle driver not being carried out by the braking and/or steering actuators. A further problem that would occur upon failure of the drive energy store is the supply of electric current to electrically-actuatable coolant actuators or coolant pumps. A failure of the drive energy store may result in overheating and destruction of the main engine and power electronic components assigned thereto.